The proposed research is to examine and to delineate physiologic regulations (Neuroendocrine function) and tissue injuries (serum enzymes) in microwave exposed rats free of non-specfic stresses. The quantitative relation among power densities, body temperatures and neuroendocrine functions or tissue injuries will be assessed. Specific attention will be paid to the interrelationships of hypothalamic-hypophysial/thyroid/adrenal/ somatotrophic axes in the animal subjected to microwave energy exposure. The interaction of previous exposure on responses or injuries, of rats to subsequent exposure will be investigated. Recovery or manifestation of acute neuroendocrine perturbance and tissue injuries by microwave exposure will be attempted. Rats will be acclimated to experimental procedures. A 3-hour equilibrium period will be given before each microwave exposure. The proposed project will extend from single to repeated (60 times, 4 hours daily) exposure to 2450 MHz (CW) microwaves in the far-field at 0.1 to 40 mW/cm2 or the equivalent specific absorption rate. Absorption rate will be determined for inter-species and inter-laboratory rate. The exposure techniques (single-vs.multi-body) will be compared.